summaryrefslogtreecommitdiffstats
path: root/browser/components/sessionstore/SessionFile.sys.mjs
blob: a44a662e07adea0e2686f485634344440beedc35 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

/**
 * Implementation of all the disk I/O required by the session store.
 * This is a private API, meant to be used only by the session store.
 * It will change. Do not use it for any other purpose.
 *
 * Note that this module depends on SessionWriter and that it enqueues its I/O
 * requests and never attempts to simultaneously execute two I/O requests on
 * the files used by this module from two distinct threads.
 * Otherwise, we could encounter bugs, especially under Windows,
 * e.g. if a request attempts to write sessionstore.js while
 * another attempts to copy that file.
 */

const lazy = {};

ChromeUtils.defineESModuleGetters(lazy, {
  sessionStoreLogger: "resource:///modules/sessionstore/SessionLogger.sys.mjs",
  RunState: "resource:///modules/sessionstore/RunState.sys.mjs",
  SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
  SessionWriter: "resource:///modules/sessionstore/SessionWriter.sys.mjs",
});

const PREF_UPGRADE_BACKUP = "browser.sessionstore.upgradeBackup.latestBuildID";
const PREF_MAX_UPGRADE_BACKUPS =
  "browser.sessionstore.upgradeBackup.maxUpgradeBackups";

const PREF_MAX_SERIALIZE_BACK = "browser.sessionstore.max_serialize_back";
const PREF_MAX_SERIALIZE_FWD = "browser.sessionstore.max_serialize_forward";

export var SessionFile = {
  /**
   * Read the contents of the session file, asynchronously.
   */
  read() {
    return SessionFileInternal.read();
  },
  /**
   * Write the contents of the session file, asynchronously.
   * @param aData - May get changed on shutdown.
   */
  write(aData) {
    return SessionFileInternal.write(aData);
  },
  /**
   * Wipe the contents of the session file, asynchronously.
   */
  wipe() {
    return SessionFileInternal.wipe();
  },

  /**
   * Return the paths to the files used to store, backup, etc.
   * the state of the file.
   */
  get Paths() {
    return SessionFileInternal.Paths;
  },
};

Object.freeze(SessionFile);

const profileDir = PathUtils.profileDir;

var SessionFileInternal = {
  Paths: Object.freeze({
    // The path to the latest version of sessionstore written during a clean
    // shutdown. After startup, it is renamed `cleanBackup`.
    clean: PathUtils.join(profileDir, "sessionstore.jsonlz4"),

    // The path at which we store the previous version of `clean`. Updated
    // whenever we successfully load from `clean`.
    cleanBackup: PathUtils.join(
      profileDir,
      "sessionstore-backups",
      "previous.jsonlz4"
    ),

    // The directory containing all sessionstore backups.
    backups: PathUtils.join(profileDir, "sessionstore-backups"),

    // The path to the latest version of the sessionstore written
    // during runtime. Generally, this file contains more
    // privacy-sensitive information than |clean|, and this file is
    // therefore removed during clean shutdown. This file is designed to protect
    // against crashes / sudden shutdown.
    recovery: PathUtils.join(
      profileDir,
      "sessionstore-backups",
      "recovery.jsonlz4"
    ),

    // The path to the previous version of the sessionstore written
    // during runtime (e.g. 15 seconds before recovery). In case of a
    // clean shutdown, this file is removed.  Generally, this file
    // contains more privacy-sensitive information than |clean|, and
    // this file is therefore removed during clean shutdown.  This
    // file is designed to protect against crashes that are nasty
    // enough to corrupt |recovery|.
    recoveryBackup: PathUtils.join(
      profileDir,
      "sessionstore-backups",
      "recovery.baklz4"
    ),

    // The path to a backup created during an upgrade of Firefox.
    // Having this backup protects the user essentially from bugs in
    // Firefox or add-ons, especially for users of Nightly. This file
    // does not contain any information more sensitive than |clean|.
    upgradeBackupPrefix: PathUtils.join(
      profileDir,
      "sessionstore-backups",
      "upgrade.jsonlz4-"
    ),

    // The path to the backup of the version of the session store used
    // during the latest upgrade of Firefox. During load/recovery,
    // this file should be used if both |path|, |backupPath| and
    // |latestStartPath| are absent/incorrect.  May be "" if no
    // upgrade backup has ever been performed. This file does not
    // contain any information more sensitive than |clean|.
    get upgradeBackup() {
      let latestBackupID = SessionFileInternal.latestUpgradeBackupID;
      if (!latestBackupID) {
        return "";
      }
      return this.upgradeBackupPrefix + latestBackupID;
    },

    // The path to a backup created during an upgrade of Firefox.
    // Having this backup protects the user essentially from bugs in
    // Firefox, especially for users of Nightly.
    get nextUpgradeBackup() {
      return this.upgradeBackupPrefix + Services.appinfo.platformBuildID;
    },

    /**
     * The order in which to search for a valid sessionstore file.
     */
    get loadOrder() {
      // If `clean` exists and has been written without corruption during
      // the latest shutdown, we need to use it.
      //
      // Otherwise, `recovery` and `recoveryBackup` represent the most
      // recent state of the session store.
      //
      // Finally, if nothing works, fall back to the last known state
      // that can be loaded (`cleanBackup`) or, if available, to the
      // backup performed during the latest upgrade.
      let order = ["clean", "recovery", "recoveryBackup", "cleanBackup"];
      if (SessionFileInternal.latestUpgradeBackupID) {
        // We have an upgradeBackup
        order.push("upgradeBackup");
      }
      return order;
    },
  }),

  // Number of attempted calls to `write`.
  // Note that we may have _attempts > _successes + _failures,
  // if attempts never complete.
  // Used for error reporting.
  _attempts: 0,

  // Number of successful calls to `write`.
  // Used for error reporting.
  _successes: 0,

  // Number of failed calls to `write`.
  // Used for error reporting.
  _failures: 0,

  // `true` once we have initialized SessionWriter.
  _initialized: false,

  // A string that will be set to the session file name part that was read from
  // disk. It will be available _after_ a session file read() is done.
  _readOrigin: null,

  // `true` if the old, uncompressed, file format was used to read from disk, as
  // a fallback mechanism.
  _usingOldExtension: false,

  // The ID of the latest version of Gecko for which we have an upgrade backup
  // or |undefined| if no upgrade backup was ever written.
  get latestUpgradeBackupID() {
    try {
      return Services.prefs.getCharPref(PREF_UPGRADE_BACKUP);
    } catch (ex) {
      return undefined;
    }
  },

  async _readInternal(useOldExtension) {
    Services.telemetry.setEventRecordingEnabled("session_restore", true);
    let result;
    let noFilesFound = true;
    this._usingOldExtension = useOldExtension;

    // Attempt to load by order of priority from the various backups
    for (let key of this.Paths.loadOrder) {
      let corrupted = false;
      let exists = true;
      try {
        let path;
        let startMs = Date.now();

        let options = {};
        if (useOldExtension) {
          path = this.Paths[key]
            .replace("jsonlz4", "js")
            .replace("baklz4", "bak");
        } else {
          path = this.Paths[key];
          options.decompress = true;
        }
        let source = await IOUtils.readUTF8(path, options);
        let parsed = JSON.parse(source);

        if (parsed._cachedObjs) {
          try {
            let cacheMap = new Map(parsed._cachedObjs);
            for (let win of parsed.windows.concat(
              parsed._closedWindows || []
            )) {
              for (let tab of win.tabs.concat(win._closedTabs || [])) {
                tab.image = cacheMap.get(tab.image) || tab.image;
              }
            }
          } catch (e) {
            // This is temporary code to clean up after the backout of bug
            // 1546847. Just in case there are problems in the format of
            // the parsed data, continue on. Favicons might be broken, but
            // the session will at least be recovered
            lazy.sessionStoreLogger.error(e);
          }
        }

        if (
          !lazy.SessionStore.isFormatVersionCompatible(
            parsed.version || [
              "sessionrestore",
              0,
            ] /* fallback for old versions*/
          )
        ) {
          // Skip sessionstore files that we don't understand.
          lazy.sessionStoreLogger.warn(
            "Cannot extract data from Session Restore file ",
            path,
            ". Wrong format/version: " + JSON.stringify(parsed.version) + "."
          );
          Services.telemetry.recordEvent(
            "session_restore",
            "backup_can_be_loaded",
            "session_file",
            null,
            {
              can_load: "false",
              path_key: key,
              loadfail_reason:
                "Wrong format/version: " + JSON.stringify(parsed.version) + ".",
            }
          );
          continue;
        }
        result = {
          origin: key,
          source,
          parsed,
          useOldExtension,
        };
        Services.telemetry.recordEvent(
          "session_restore",
          "backup_can_be_loaded",
          "session_file",
          null,
          {
            can_load: "true",
            path_key: key,
            loadfail_reason: "N/A",
          }
        );
        Services.telemetry
          .getHistogramById("FX_SESSION_RESTORE_CORRUPT_FILE")
          .add(false);
        Services.telemetry
          .getHistogramById("FX_SESSION_RESTORE_READ_FILE_MS")
          .add(Date.now() - startMs);
        lazy.sessionStoreLogger.debug(`Successful file read of ${key} file`);
        break;
      } catch (ex) {
        if (DOMException.isInstance(ex) && ex.name == "NotFoundError") {
          exists = false;
          Services.telemetry.recordEvent(
            "session_restore",
            "backup_can_be_loaded",
            "session_file",
            null,
            {
              can_load: "false",
              path_key: key,
              loadfail_reason: "File doesn't exist.",
            }
          );
          // A file not existing can be normal and expected.
          lazy.sessionStoreLogger.debug(
            `Can't read session file which doesn't exist: ${key}`
          );
        } else if (
          DOMException.isInstance(ex) &&
          ex.name == "NotAllowedError"
        ) {
          // The file might be inaccessible due to wrong permissions
          // or similar failures. We'll just count it as "corrupted".
          lazy.sessionStoreLogger.error(
            `NotAllowedError when reading session file: ${key}`,
            ex
          );
          corrupted = true;
          Services.telemetry.recordEvent(
            "session_restore",
            "backup_can_be_loaded",
            "session_file",
            null,
            {
              can_load: "false",
              path_key: key,
              loadfail_reason: ` ${ex.name}: Could not read session file`,
            }
          );
        } else if (ex instanceof SyntaxError) {
          lazy.sessionStoreLogger.error(
            "Corrupt session file (invalid JSON found) ",
            ex,
            ex.stack
          );
          // File is corrupted, try next file
          corrupted = true;
          Services.telemetry.recordEvent(
            "session_restore",
            "backup_can_be_loaded",
            "session_file",
            null,
            {
              can_load: "false",
              path_key: key,
              loadfail_reason: ` ${ex.name}: Corrupt session file (invalid JSON found)`,
            }
          );
        }
      } finally {
        if (exists) {
          noFilesFound = false;
          Services.telemetry
            .getHistogramById("FX_SESSION_RESTORE_CORRUPT_FILE")
            .add(corrupted);
          Services.telemetry.recordEvent(
            "session_restore",
            "backup_can_be_loaded",
            "session_file",
            null,
            {
              can_load: (!corrupted).toString(),
              path_key: key,
              loadfail_reason: "N/A",
            }
          );
        }
      }
    }
    return { result, noFilesFound };
  },

  // Find the correct session file and read it.
  async read() {
    // Load session files with lz4 compression.
    let { result, noFilesFound } = await this._readInternal(false);
    if (!result) {
      // No result? Probably because of migration, let's
      // load uncompressed session files.
      let r = await this._readInternal(true);
      result = r.result;
    }

    // All files are corrupted if files found but none could deliver a result.
    let allCorrupt = !noFilesFound && !result;
    Services.telemetry
      .getHistogramById("FX_SESSION_RESTORE_ALL_FILES_CORRUPT")
      .add(allCorrupt);

    if (!result) {
      // If everything fails, start with an empty session.
      lazy.sessionStoreLogger.warn(
        "No readable session files found to restore, starting with empty session"
      );
      result = {
        origin: "empty",
        source: "",
        parsed: null,
        useOldExtension: false,
      };
    }
    this._readOrigin = result.origin;

    result.noFilesFound = noFilesFound;

    return result;
  },

  // Initialize SessionWriter and return it as a resolved promise.
  getWriter() {
    if (!this._initialized) {
      if (!this._readOrigin) {
        return Promise.reject(
          "SessionFileInternal.getWriter() called too early! Please read the session file from disk first."
        );
      }

      this._initialized = true;
      lazy.SessionWriter.init(
        this._readOrigin,
        this._usingOldExtension,
        this.Paths,
        {
          maxUpgradeBackups: Services.prefs.getIntPref(
            PREF_MAX_UPGRADE_BACKUPS,
            3
          ),
          maxSerializeBack: Services.prefs.getIntPref(
            PREF_MAX_SERIALIZE_BACK,
            10
          ),
          maxSerializeForward: Services.prefs.getIntPref(
            PREF_MAX_SERIALIZE_FWD,
            -1
          ),
        }
      );
    }

    return Promise.resolve(lazy.SessionWriter);
  },

  write(aData) {
    if (lazy.RunState.isClosed) {
      return Promise.reject(new Error("SessionFile is closed"));
    }

    let isFinalWrite = false;
    if (lazy.RunState.isClosing) {
      // If shutdown has started, we will want to stop receiving
      // write instructions.
      isFinalWrite = true;
      lazy.RunState.setClosed();
    }

    let performShutdownCleanup =
      isFinalWrite && !lazy.SessionStore.willAutoRestore;

    this._attempts++;
    let options = { isFinalWrite, performShutdownCleanup };
    let promise = this.getWriter().then(writer => writer.write(aData, options));

    // Wait until the write is done.
    promise = promise.then(
      msg => {
        // Record how long the write took.
        this._recordTelemetry(msg.telemetry);
        this._successes++;
        if (msg.result.upgradeBackup) {
          // We have just completed a backup-on-upgrade, store the information
          // in preferences.
          Services.prefs.setCharPref(
            PREF_UPGRADE_BACKUP,
            Services.appinfo.platformBuildID
          );
        }
      },
      err => {
        // Catch and report any errors.
        console.error("Could not write session state file ", err, err.stack);
        this._failures++;
        // By not doing anything special here we ensure that |promise| cannot
        // be rejected anymore. The shutdown/cleanup code at the end of the
        // function will thus always be executed.
      }
    );

    // Ensure that we can write sessionstore.js cleanly before the profile
    // becomes unaccessible.
    IOUtils.profileBeforeChange.addBlocker(
      "SessionFile: Finish writing Session Restore data",
      promise,
      {
        fetchState: () => ({
          options,
          attempts: this._attempts,
          successes: this._successes,
          failures: this._failures,
        }),
      }
    );

    // This code will always be executed because |promise| can't fail anymore.
    // We ensured that by having a reject handler that reports the failure but
    // doesn't forward the rejection.
    return promise.then(() => {
      // Remove the blocker, no matter if writing failed or not.
      IOUtils.profileBeforeChange.removeBlocker(promise);

      if (isFinalWrite) {
        Services.obs.notifyObservers(
          null,
          "sessionstore-final-state-write-complete"
        );
      }
    });
  },

  async wipe() {
    const writer = await this.getWriter();
    await writer.wipe();
    // After a wipe, we need to make sure to re-initialize upon the next read(),
    // because the state variables as sent to the writer have changed.
    this._initialized = false;
  },

  _recordTelemetry(telemetry) {
    for (let id of Object.keys(telemetry)) {
      let value = telemetry[id];
      let samples = [];
      if (Array.isArray(value)) {
        samples.push(...value);
      } else {
        samples.push(value);
      }
      let histogram = Services.telemetry.getHistogramById(id);
      for (let sample of samples) {
        histogram.add(sample);
      }
    }
  },
};